The back pressure of flash column is related to the particle size of packed material. The packed material with smaller particle size will result in higher back pressure for the flash column. Therefore the flow rate of the mobile phase used in flash chromatography should be lowered accordingly in order to prevent the flash system from stop working.
The back pressure of flash column is also proportional to the length of column. Longer column body will result in higher back pressure for the flash column. Furthermore, the back pressure of flash column is inversely proportional to the ID (internal diameter) of the column body. Finally, the back pressure of flash column is proportional to the viscosity of the mobile phase used in flash chromatography.
Possible causes:
- Sample concentration is too low.
- Analytes are not UV-active or lack chromophores.
Solution: Concentrate the sample or use a staining reagent.
The plate is tilted during development.
Solvent evaporation during development.
Solution: Ensure the plate is level and use a saturated chamber.
Possible causes:
- Overloading the sample.
- Using an inappropriate solvent system.
- Poor sample solubility.
Solution: Dilute the sample, optimize the solvent system, or ensure complete dissolution.
Most TLC plates can tolerate up to 200°C during drying. Always refer to the manufacturer’s guidelines.
Yes, many plates are pre-coated with UV254 or UV366 indicators to aid visualization under UV light.
Particle size is typically 5 – 20 µm. Analytical TLC layers are usually 250 µm (0.25 mm) thick, while preparative layers are 500 – 2,000 µm (0.5 – 2 mm) thick.
Use a capillary tube or micropipette to spot small, consistent volumes (1 – 2 µL) on the baseline. Ensure spots are evenly spaced.
Use UV light for fluorescent indicators, iodine vapors for certain organic compounds, or chemical stains like ninhydrin or sulfuric acid for others.
TLC plates are generally single-use due to contamination. For training or non-critical uses, plates can sometimes be cleaned and reused with solvents.
